<template>
  <div class="spec-preview">
    <img :src="defaultImg.imgUrl" />
    <div class="event" @mousemove="move"></div>
    <div class="big">
      <img :src="defaultImg.imgUrl" ref="bigImage"/>
    </div>
    <div class="mask" ref="mask"></div>
  </div>
</template>

<script>
  export default {
    name: "Zoom",
    props:['imageList'],
    data(){
      return {
        defaultIndex: 0,
      }
    },
    mounted(){
        this.$bus.$on('changeDefaultIndex',this.changeDefaultIndex);
    },
    computed:{
        defaultImg(){
          return this.imageList[this.defaultIndex] || {}
        },
    },
    methods:{
      changeDefaultIndex(index){
          this.defaultIndex = index;
      },
      move(event){
        // 获取鼠标的位置
        let mask = this.$refs.mask
        let bigImage = this.$refs.bigImage
        let moveX = event.offsetX;
        let moveY = event.offsetY;
        let maskX = moveX - mask.offsetWidth/2;
        let maskY = moveY - mask.offsetHeight/2;
        mask.style.left = Math.max(maskX < mask.offsetWidth ? maskX:mask.offsetWidth,0)+'px';
        mask.style.top = Math.max(maskY < mask.offsetHeight ? maskY:mask.offsetHeight,0)+'px';
        bigImage.style.left = -2*maskX+"px";
        bigImage.style.top = -2*maskY+"px";
      },
    },
  }
</script>

<style lang="less">
  .spec-preview {
    position: relative;
    width: 400px;
    height: 400px;
    border: 1px solid #ccc;

    img {
      width: 100%;
      height: 100%;
    }

    .event {
      width: 100%;
      height: 100%;
      position: absolute;
      top: 0;
      left: 0;
      z-index: 998;
    }

    .mask {
      width: 50%;
      height: 50%;
      background-color: rgba(0, 255, 0, 0.3);
      position: absolute;
      left: 0;
      top: 0;
      display: none;
    }

    .big {
      width: 100%;
      height: 100%;
      position: absolute;
      top: -1px;
      left: 100%;
      border: 1px solid #aaa;
      overflow: hidden;
      z-index: 998;
      display: none;
      background: white;

      img {
        width: 200%;
        max-width: 200%;
        height: 200%;
        position: absolute;
        left: 0;
        top: 0;
      }
    }

    .event:hover~.mask,
    .event:hover~.big {
      display: block;
    }
  }
</style>